Sound Tools

Twenty-three tools for a sound file, and the recording never leaves the tab

A recording is the most personal thing in this workspace: it carries a voice, a room, and whatever happened to be said while it was running. The whole application is WebAssembly, it runs on your own device, and there is no server to send a recording to.

Nothing here listens, and nothing here plays. Half of what a search for these tools turns up is real-time — a metronome that ticks, a tuner that hears an instrument, a recorder — and this framework has no audio output, no microphone and no clock. So the metronome writes a click track, the tuner tunes a file, and the ear trainer writes the interval down. Each of them says so on its own result rather than drawing a button that would not work.

Only WAV is opened whole. MP3, FLAC, Ogg, AAC and AIFF are recognised and their headers are read and described, but a decoder for any one of them is a larger program than this whole application — so a tool that needs samples names the format it was given and refuses, rather than producing something plausible.

There is no sample recording, because this workspace ships no binary files at all. The example button synthesises what it needs and says so, which is the better fixture as well: a computed sound is identical every time, so a comparison between two settings is a comparison between two settings.

Make a sound

Tone generator
A steady tone of any shape and frequency, written as a file to play elsewhere.

Noise generator
White, pink and brown are three genuinely different things, and the slope of each is on the result.

Frequency sweep
A tone that slides from one frequency to another, logarithmically, because pitch is a ratio.

Binaural beats
Two near tones, one to each ear. What the file contains is certain; what it is claimed to do is not.

Click track
A metronome as a file: a fixed tempo with the first beat accented, and it will not follow you.

Morse code audio
Text sent as Morse at a stated speed, with Farnsworth timing and the code written out beside it.

Intervals and chords
An interval or a chord written out to play, together or one note at a time.

Change a recording

Reverse audio
Backwards, whole or in part, and the only operation here that loses nothing at all.

Fade in and out
A fade at each end, with the curve that keeps a crossfade even rather than the one that dips.

Normalise the level
To a target peak or a target loudness, which are different numbers, with headroom left for the encoder.

Remove the silence
Finds the quiet stretches and shortens them, keeping enough of each that two words do not run together.

Speed and sample rate
Two different things people ask for as one: playing faster raises the pitch, and resampling does not.

Split the channels
Mono, one side, swapped or panned, with a word about what summing cancels.

Read a recording

Sound file info
Format, rate, channels, length and bit rate, read from the header — of six formats, not one.

Levels and dynamics
The peak, the loudness and the gap between them, which is the number that says what kind of recording it is.

Waveform image
The shape of a recording as an SVG, drawn from peaks because every sample would be a solid block.

Spectrum analyser
Which frequencies one moment holds, with the trade between time and frequency stated in numbers.

Find the pitch
What note a recording is playing, in cents, at whichever concert A you use. A tuner for a file, not a string.

Pitch and tempo

Note frequency table
Every note and its frequency, at 440 or 415 or whatever you tune to, with the difference in cents.

Delay and reverb times
A tempo turned into milliseconds for every note length, dotted and triplet included.

Tempo from tap times
Paste the times from anywhere — a stopwatch, a marker list, a video's timecodes — and it does a tapper's arithmetic.

Cents and intervals
The distance between two pitches, and how far equal temperament is from the pure ratios.

Sound level and exposure
How long a level is safe for, and why two equally loud sources are three decibels louder rather than twice.

Questions

Why is there no recorder?: Because recording is the one thing that would need a permission, and a tool that asks for a microphone is a different promise from one that cannot. Everything here starts from a file you already have or a sound it computes, and the browser never prompts you.
How large a file can I open?: Thirty-two megabytes, checked from the file's own header before the samples are read, and the refusal carries the size it found. That is about three minutes of CD-quality stereo, or twenty of mono speech.
Is the loudness meter the same as LUFS?: No, and it says so on every result. A broadcast measurement weights the spectrum by hearing and gates the quiet parts; this does neither. Use it to compare two recordings with each other, not to meet a delivery specification.
Why does changing the speed change the pitch?: Because that is what changing the speed does, exactly as a tape does it. Keeping the pitch while changing the length is a time-stretch, and it is a much larger piece of code than this whole application — so nothing here claims to do it.